This invention relates to core drilling and more particularly to apparatus and methods for determining the original orientation of a core sample after it has been drilled, separated and pulled out of the earth.
Many forms of geological survey depend on core drilling for samples. Some surveying requires that the orientation of a core be determined accurately and reliably. In many situations the angle of the longitudinal axis of the core drill relative to the xe2x80x9cplanexe2x80x9d of the earth at the drill site is other than 90 degrees. This is the drilling angle and it may be ascertained in a number of ways. It is sometimes also important to determine, after removing the core for inspection, the rotational orientation or compass orientation of the core sample relative to the surrounding terrain from which it was extracted. Known prior methods are not reliable, particularly at low angles of inclination from the vertical.
It is an object of the invention to provide an apparatus for use with core drilling devices which includes a hard ball which runs in a circumferential track. The ball and track are adapted to be carried within a tubular upper end casing, which surrounds the spindle which supports the inner tube of the drill. An indent washer is positionable above the track and ball and is oriented relative to the casing. A spring supports the washer above the ball. When the upper end is lifted, the ball is driven into contact with the washer and makes an impression. The orientation of the impression reveals the orientation of the lowest point in the track. The impressioned washer can be used to assist in noting or marking the core orientation after the drill is removed from the earth.
In one preferred embodiment of the invention, the washer is formed with an alignment hole. The upper end casing supports a pin which extends in the direction of the drill rotational axis. The pin passes through the hole to maintain the washer in a fixed alignment with the casing.
In another embodiment of the invention the spindle is split into upper and lower segments, the lower segment having a flange which bears on thrust bearings.
In another embodiment of the invention, a laser pointer system is used to transfer orientation information to a core which has been drilled in conjunction with a ball, track and washer device as disclosed with reference to the present invention.
It is yet another object of the invention to provide an apparatus for use with core drilling devices which includes a pendulum and backing plate which together form a ball and socket joint. The pendulum terminates in the joint which makes an impression in the indent washer having a known orientation.